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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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This report presents the results of a series of negative thrust and torque measurements made with a 4 foot diameter model of a conventional aluminum-alloy propeller. The tests were made in the 20-foot propeller-research tunnel of the National Advisory Committee for Aeronautics. The results show that the negative thrust is considerably affected by the shape and size of the body behind the propeller, that the maximum negative thrust increases with decrease in blade-angle setting, and that the drag of a locked propeller may be greatly reduced by feathering it into the wind. Several examples of possible applications of the data are given.
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This report treats the following problems: The beginning of the investigated motions is always a setting of the lateral controls, i.e., the rudder or the ailerons. Now, the first interesting question is how the motion would proceed if these settings were kept unchanged for some time; and particularly, what upward motion would set in, how soon, and for how long, since therein lie the dangers of yawing. Two different motions ensue with a high rate of turn and a steep down slope of flight path in both but a marked difference in angle of attack and consequently different character in the resultant aerodynamic forces: one, the "corkscrew" dive at normal angle, and the other, the "spin" at high angle.
The objective of this work is to develop techniques for the control and management of separated flows over airfoils, particularly under unsteady operating conditions. The results are expected to help achieve the ultimate goal, which is flow management for highly maneuverable aircraft.
The Control System for the Mod-2 wind turbine system is required to provide not only for startup, RPM regulation, maximizing or regulating power, and stopping the rotor, but also for load limiting, especially in the power train. Early operations with above-rated winds revealed an instability which was caused primarily by coupling between the quill shaft and the rotor air loads. This instability caused the first of several major Mod-2 Control System changes which are reviewed in the paper.
Results of recent experimental studies into the effect of compressibility on dynamic stall of oscillating airfoils are reviewed. Stroboscopic schlieren images of the strongly unsteady flow field are presented, showing the development of the dynamic stall vortex, and its progression down the airfoil. The effect of varying free-stream Mach number and frequency of oscillation of the airfoil are demonstrated, and examples of local supersonic flow are presented, including the presence of a shock near the leading edge of the airfoil.
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Aerodynamic coefficients are presented for perfect-gas and equilibrium-air solutions of the Navier-Stokes equations about the Stardust reentry-capsule forebody at Mach numbers of 4.6, 7, 8.5, and 10. A comparison with Newtonian-flow assumptions indicates a divergence of the aerodynamic coefficients from Newtonian-flow for Mach numbers less than 10. The static stability of the forebody is reduced by a factor of 2.5 with decreasing freestream Mach number between Mach 10 and 7.